Because of their low power consumption, high luminance and high durability, light emitting diodes (LEDs) are in the spotlight as a light source for an illumination apparatus with which incandescent lamps, fluorescent lamps and the like are replaced. However, since a single LED provides less light intensity than a fluorescent lamp, a light emitting device including a plurality of LEDs is used for a general illumination apparatus having LEDs as a light source.
As one example of LED packages for such a type of light emitting device, there has been known an LED package in which a yellow fluorescent-material layer is coated on an LED chip emitting a blue light, wherein the blue light and a yellow light are mixed to thereby realize a white light (see, e.g., Japanese Patent Application Publication No. 2011-014695 (JP2011-014695A)). In addition, as shown in FIG. 10A, there has been proposed an LED package 101 in which an LED chip is coated with a hemispherical resin layer 104 containing a fluorescent material (see, e.g., Japanese Patent Application Publication No. 2008-135707 (JP2008-135707A)). Further, as shown in FIG. 11A, there has been proposed an illumination apparatus 110 in which a plurality of LED packages 101 having respective hemispherical transparent resin parts 104 is arranged and a diffusion and transmission panel 107 is disposed adjacent to the front side of the LED packages 101.
However, in the light emitting device disclosed in JP2011-014695A and JP2008-135707, since an output surface of the yellow fluorescent-material layer mounted on the LED package has a planar or hemispherical shape, the distribution of emitted lights has a high directivity in a light output direction, as shown in FIG. 10B. That is, light intensity in the front direction of the LED package is high while light intensity in the circumferential direction thereof is low. Therefore, even if a reflector is provided to cover the LED package, it is difficult to control the distribution of lights since the amount of lights incident into the reflector is low.
In addition, in the above-mentioned illumination apparatus 110, luminance of portions immediately above the LED packages 101 becomes increased. This results in a non-uniform distribution of luminance at the output surface (the diffusion and transmission panel 107) of the illumination apparatus, thereby resulting in a granule-like distribution of the lights, and causing surface reflection.